Thai built d40 wont start unless fuel is primed

[Cairnsy 80]

Hi gents, long post ... im having issus with my 2012 d40 not starting unless i pump the primer up then it will run and drive perfectly, no smoke or lack of power. Iv fitted a new filter head and filter replaced all the hoses to the inj pump still no good.. the primer goes soft after a few mins of sittiing. Iv by passed the filter head and used a 3/8 grenade primer but still the same iv also fitted a non return valve in the supply line to the filter head. Iv found if i remove the return from the steel pipe at the bulk head and plug it with a punch it will stay primed for days and will start on the button ( only run for a sec) i undedstand that when priming you are also purging the air from the system there for you will get fuel travelling back to the tank, however why does if carry on until the priming pressure drops away?

 

[Phunk]

you sure there isn't a kink in the line or a leak somewhere? if you're having to prime each time you start the car you're losing fuel from the inlet side.

Do these cars have an in-tank pump or an inline low pressure pump to push fuel to the filter?

 

[Cairnsy 80]

Yeah, no kinks etc. They dont have any sort of low pressure pump, as in this particular common rail it only needs a supply of fuel under minimal pressure from the primer and when the engine is cranked it genertes the high pressure needed for injection.

 

[Cairnsy 80]

Found this image and cannot find out if the return has a mechanical spring to close off when the fuel pressure drops to the required level? As mine just stays open and dribbles until all pressure is lost in the primer. As i say if i plug it the primer stays rock hard so no leaks etc. Thanks guys frustration is getting the better of me.

 

[Phunk]

Found this image and cannot find out if the return has a mechanical spring to close off when the fuel pressure drops to the required level? As mine just stays open and dribbles until all pressure is lost in the primer. As i say if i plug it the primer stays rock hard so no leaks etc. Thanks guys frustration is getting the better of me.

this is actually a great diagram and I've learned a lot from this. Learned that there is no pre-pump that I can see.

I know I'll be corrected if I'm wrong, but it may actually be the dreaded Suction Control Valve, its job is to manage pressure

 

[Nig]

Rail preasure valve could be faulty.

 

[Old.Tony]

Let me try and get this clear: when the engine starts and continues, it doesn't hesitate or falter in any way at all. The problem occurs if the engine is stopped and left not running for a period, then it needs to be primed again?

My own car did this. There's a common cause for this (not saying it can't be something else, but commonly...) and there's an easy way to find out where.

The fuel pump sits low on the engine, the fuel filter sits up high in the bay, and the tank sits low at the back of the car. This means the filter is at the high point (along with the water sensor and primer). Because all of the fuel system is under very low pressure, you'll normally never see any diesel fuel leaks from the section from the tank through the filter to the pump. However, if there's a tiny hole/gap/split, air can make its way in.

I've had this happen because a mechanic (yeah, a real one) didn't do up the water sensor properly in the fuel filter. The electrical connection for the sensor is supposed to line up with the knurled knob on the front of the filter. It's supposed to be a firm 'click' into place. I've also had this happen because one of the hoses aged and cracked just a little. I had to prime the fuel system every morning before driving. If I primed it heaps, I'd end up with diesel on my hand - because it pressurised the system and allowed diesel to leak out.

And that's how you find it. Prime it, and keep priming it. I probably pumped mine about 30 times before diesel started dripping from under the filter, but it pointed to a small crack in one of the fuel hoses at the top.

Let's hope yours is as easy.

 

[Nig]

Turn the primer plunger, if the palm button turns it wont hold pressure, tighten the phillips screw that holds it on, this will seal it propper,

 

[Phunk]

Let me try and get this clear: when the engine starts and continues, it doesn't hesitate or falter in any way at all. The problem occurs if the engine is stopped and left not running for a period, then it needs to be primed again?

My own car did this. There's a common cause for this (not saying it can't be something else, but commonly...) and there's an easy way to find out where.

The fuel pump sits low on the engine, the fuel filter sits up high in the bay, and the tank sits low at the back of the car. This means the filter is at the high point (along with the water sensor and primer). Because all of the fuel system is under very low pressure, you'll normally never see any diesel fuel leaks from the section from the tank through the filter to the pump. However, if there's a tiny hole/gap/split, air can make its way in.

I've had this happen because a mechanic (yeah, a real one) didn't do up the water sensor properly in the fuel filter. The electrical connection for the sensor is supposed to line up with the knurled knob on the front of the filter. It's supposed to be a firm 'click' into place. I've also had this happen because one of the hoses aged and cracked just a little. I had to prime the fuel system every morning before driving. If I primed it heaps, I'd end up with diesel on my hand - because it pressurised the system and allowed diesel to leak out.

And that's how you find it. Prime it, and keep priming it. I probably pumped mine about 30 times before diesel started dripping from under the filter, but it pointed to a small crack in one of the fuel hoses at the top.

Let's hope yours is as easy.

Does the Thai model have that same sensor as the VSK under the filter?

 

[Cairnsy 80]

Let me try and get this clear: when the engine starts and continues, it doesn't hesitate or falter in any way at all. The problem occurs if the engine is stopped and left not running for a period, then it needs to be primed again?

My own car did this. There's a common cause for this (not saying it can't be something else, but commonly...) and there's an easy way to find out where.

The fuel pump sits low on the engine, the fuel filter sits up high in the bay, and the tank sits low at the back of the car. This means the filter is at the high point (along with the water sensor and primer). Because all of the fuel system is under very low pressure, you'll normally never see any diesel fuel leaks from the section from the tank through the filter to the pump. However, if there's a tiny hole/gap/split, air can make its way in.

I've had this happen because a mechanic (yeah, a real one) didn't do up the water sensor properly in the fuel filter. The electrical connection for the sensor is supposed to line up with the knurled knob on the front of the filter. It's supposed to be a firm 'click' into place. I've also had this happen because one of the hoses aged and cracked just a little. I had to prime the fuel system every morning before driving. If I primed it heaps, I'd end up with diesel on my hand - because it pressurised the system and allowed diesel to leak out.

And that's how you find it. Prime it, and keep priming it. I probably pumped mine about 30 times before diesel started dripping from under the filter, but it pointed to a small crack in one of the fuel hoses at the top.

Let's hope yours is as easy.

Hi old tony,

Yes you are correct it does not fault once started plenty of power no smoke etc. Thats why i dont think its the SCV.
Iv had two new filters on it new orings on the water sensor etc. I know the fiter head etc isnt the fault because i temporeraly deleted it by putting 3/8 boat primer bulb between the inlet and outlet and it still faulted. If i plug the return hose and pump the primer rock hard and it will remain like that for days, The engine will start on the button too.
If i reconnect everything back together and pull the return off and put it into a clear container, when i pump the primer the fuel flows as normal bleeding any air but when i stop pumping the fuel continues to dribble out untill all pressure is lost in the primer. I would like to think that it would stop soon after i stopped pumping?
Thanks..

 

[Old.Tony]

Okay, so it's not the filter at all (my own recent leak wasn't the filter, it was the hose connected to the filter).

If you overprime it (with everything returned to normal, and just prime the thing like crazy) does it leak fuel?

 

[Cairnsy 80]

Okay, so it's not the filter at all (my own recent leak wasn't the filter, it was the hose connected to the filter).

If you overprime it (with everything returned to normal, and just prime the thing like crazy) does it leak fuel?

No mate, if i prime it with it all back together there are no leaks any where and i can get the primer to go hard, but after 10 mins or so it goes soft again, so im guessing the accumulated pressure is just slowley leaking back to the tank via the return line instead of retaining at least enough pressure so the low pressure pump in the inj pump can take over and supply fuel to the high pressure side. Like i say the return just continues tk dribble until all priming pressure is lost.. head banger. I have another non return valve that only opens ag very low pressure so im goingbto fit it in the return and hopefully the slight resistance in then valve is enough to stop the dribble.
Will keep you posted. Its only very low kms at 76,000 so i was doughtfull of the pump but the more i think about if im steering towards it..

 

[Nig]

Pull the feed line off at the filter, M/T it ,fill it with injector cleaner replace it prime the pump and start it, see if that helps, when i do a filter chage i always squert the cleaner in the filter to do this.moght just do the trick.

 

[Old.Tony]

I might sound like a broken record here, but there's a point to it.

If the system is completely sealed, the fuel should not dribble back (at all, ever) - it's designed to remain sealed to keep the fuel there*. If the fuel is draining back, something is letting air in. If you could introduce excess pressure in the system - by continuing to prime it even though the primer is firm - you should be able to find where this problem is.

It would be very unusual for it to be the pump itself, but overpressurising the system will make the fuel leak out of where the problem is occurring so you'd be able to see if it was the pump at fault.

* Note: the fuel pump relies on diesel fuel to lubricate its internals. It's quite a sensitive device, and quite expensive. Nissan knows this, and designed the system so that - if there are no leaks - it will be lubricated and not suffer damage internally.

 

[kinell]

HI Cairnsy, i have exactly the same problem on my 2010 model, was thinking SCV but after reading this i am not so sure, please let me know if you find a solution.

 

[kinell]

Thanks old Tony mine turned out to be a split in the primer bulb.